Estimated Average Glucose (eAG) is an approximate average of blood glucose readings for three (3) months. Much of the time, your eAG matches your A1C but not always.

A1C & eAG
Estimated average glucose is a simple way to understand A1C. This provides your approximate average blood-glucose level for last three months.
http://healthy-ojas.com/diabetes/a1c-eag.html

A1C and eAG
What is the Difference Between eAG and the Average on My Monitor?
However, eAG is not the same average glucose level as the average of your readings on your meter. Because people with diabetes are more likely to check their blood glucose more often when they are low (for example, first thing in the morning and before meals), the average of the readings on their meter is likely to be lower than their eAG.
http://www.diabetes.org/living-with-diabetes/treatment-and-care/blood-glucose-control/a1c/

Understanding the eAG
Your estimated Average Glucose (eAG) number is calculated from the result of your A1c test. Like the A1c, the eAG shows what your average blood sugars have been over the previous 2 to 3 months. Instead of a percentage, the eAG is in the same units (mg/dl) as your blood glucose meter. A chart shows the relationship between the A1c percentage and the eAG.
https://www.ghc.org/healthAndWellness/?item=%2Fcommon%2FhealthAndWellness%2Fconditions%2Fdiabetes%2Fa1c.html

eAG/A1C Conversion Calculator
http://professional.diabetes.org/diapro/glucose_calc